This invention relates to wireless telecommunications services, and, in particular, to international roaming of wireless terminals.
The operation of obtaining service outside of a wireless subscriber""s home service area is commonly referred to as roaming. The ability of a subscriber to roam outside of his or her home service area depends on the relationship between the subscriber""s home service provider and the service provider in the area being visited. This relationship ideally includes the ability to exchange information between the two systems. In order to provide a consistent exchange of information, with minimal user intervention, the telecommunications industry has developed standard protocols for communications between mobile switching centers, making it possible for roaming subscribers to originate, receive, and maintain calls as they cross system boundaries.
Reference in this regard can be had, by example, to Telecommunications Industry Association Interim Standard 41 (TIA IS-41), also referred to as ANSI/TIA/EIA 41-D-1997 (ANSI-41), entitled xe2x80x9cCellular Radiotelecommunications Intersystem Operations.xe2x80x9d
ANSI-41 specifies two types of databases to facilitate roaming, the home location register (HLR) and the visitor location register (VLR). The home location register resides with the subscriber""s home service provider and contains pertinent information about the subscriber""s equipment and the services the subscriber is entitled to. The HLR also contains the current location and status of the subscriber""s terminal. Access to the HLR is controlled by the subscriber""s mobile identification number (MIN), which is stored in the terminal. The visitor location register (VLR) resides with the system being visited, referred to as the serving system, and contains information, including the MIN and the electronic serial number (ESN), regarding the terminals currently in the serving system service area.
When a terminal enters a serving system, it attempts to register in that system. As part of the registration process, the serving system""s mobile switching center (MSC) records information about the terminal, including the terminal""s MIN and ESN, in its VLR. The serving system""s VLR then attempts to contact the subscriber""s HLR for authentication that the subscriber is entitled to access the system.
ANSI-41 wireless networks worldwide use the MIN, mentioned above, to identify their subscribers within their own country. In North America, the MIN is often used as the subscriber""s mobile directory number (MDN). ANSI-41 wireless networks in the United States and Canada also use the subscriber""s 10 digit MIN to direct messages from the serving system to the subscriber""s HLR. While MIN-based routing is generally supported in the ANSI networks of North America, it is not recognized as a valid global address type, also referred to as a title, by the International Telecommunications Union (ITU). As a result, using a subscriber""s MIN to locate the subscriber""s HLR is not generally supported by networks outside of North America. Thus, a subscriber""s MIN is not necessarily a valid global title.
New protocol extensions to ANSI-41 are being developed to provide true global title formats, specifically E.212, however, since the ITU has not yet accepted E212 as an officially sanctioned translation type, the useful application of E.212 is not expected to be available globally for some time.
The International Forum for AMPS Standards Technology (I FAST) has issued unique network codes to operators outside of North America for use as the most significant four digits of their subscribers"" MINs. MINs using these special codes are called International Roaming MINs (IRMs). The use of IRMs ensures that a globally unique identification is available for mobile subscribers, and IRMs provide a generally accepted global title for directing a visited system to a subscriber""s HLR. The IRM always begins with a xe2x80x9c0xe2x80x9d or a xe2x80x9c1xe2x80x9d to ensure that they never conflict with MINs used in North America, as North American MINs never start with a xe2x80x9c0xe2x80x9d or a xe2x80x9c1.xe2x80x9d While IRMs provide a generally accepted method for designating a subscriber""s HLR, North American MINs, because they never begin with a xe2x80x9c0xe2x80x9d or xe2x80x9c1xe2x80x9d, remain unacceptable as global titles.
These problems are compounded when using a global satellite communications system, such as one shown in U.S. Pat. No. 5,655,005, issued Aug. 5, 1997, entitled xe2x80x9cWorldwide telecommunications System Using Satellitesxe2x80x9d, by Robert A. Wiedeman and Paul A. Monte and U.S. Pat. No. 5,715,297, issued Feb. 3, 1998, entitled xe2x80x9cWireless Telephone/Satellite Roaming Systemxe2x80x9d, by Robert A. Wiedeman. In a global satellite communications system, a user""s terminal is intended to have service anywhere within the coverage area of a satellite system, regardless of international boundaries.
It is an object and advantage of this invention to provide a method and apparatus to allow subscribers of ANSI-41 based networks to roam internationally. It is a second object and advantage of this invention to provide a method and apparatus to allow subscribers of ANSI-41 based networks to roam internationally by correctly routing wireless signaling messages from a visited system to a subscribers home network using the terminal""s MIN as the initial addressing format. It is a further object and advantage of this invention to provide a method and apparatus to allow subscribers of ANSI-41 based networks to roam internationally in a global satellite communications system.
The foregoing and other problems are overcome and the objects of the invention are realized by methods and apparatus in accordance with embodiments of this invention.
A method is provided for routing a message through a telecommunications network. The method includes receiving an identifying number (eg: a MIN or ESN) from a wireless terminal and prepending at least one character to the identifying number to form a pseudo-global title. The message is then routed through the telecommunications network to a destination determined by the pseudo-global title. Upon arrival at the destination, the method further includes converting the pseudo-global title to a home location register address. The message is then routed to a home location register having the home location register address.